1. Field of the Invention
This invention pertains to helper or secondary spring for use in combination in a vehicle suspension system with a primary leaf spring.
2. Description of the Prior Art
In vehicles equipped with leaf springs as the source of primary suspension, it very often happens that higher than average loads are transported, contrary to the more typical presumed load limits usually encountered. Increased loading of primary leaf springs accelerates the process of permanent deformation of such springs which, in turn, allows the vehicle body to lose its trim height, and that creates a loss of handling and further reduction in load carrying capacities.
Many different solutions have been proposed and tried, such as the overload spring disclosed in U.S. Pat. No. 2,826,407 of Mar. 11, 1958 for one example. Another example is seen in U.S. Pat. No. 3,672,656 of June 27, 1972. Then there are leaf springs formed from composite and non-metallic materials such as U.S. Pat. No. 3,900,357 of Aug. 19, 1975 and U.S. Pat. No. 4,786,033 of Nov. 22, 1988. These last two patents disclose primary leaf springs using non-metallic materials. Even with primary springs using composite non-metallic materials, it is useful to provide secondary springs to help carry added loads that may be unintentionally or intentionally loaded on. In this class is the overload spring of U.S. Pat. No. 3,039,759 of June 19, 1962.